The known countertypes of the stereoscopic projection systems (golographic, raster, with stereoscopic glasses, retroreflective and others) with the exception of the system of projection on reflecting spherical stereoscreens are discomfort and unfit for long viewing of stereoimages.
The common drawback of these countertypes is a technical problem of auto-correction and video correction of the stereoscopic system individually for each viewer.
The most close prototype both for design and reached effect is the system of stereo projection onto the reflecting spherical stereoscreen described in the invention “A Stereoscopic System” by S. I. Arsenich (RF patent No 2221350 published in October 2004). A stereoscopic projection system comprises a reflecting spherical stereoscreen, individual stereoprojectors for each viewer (for projection of stereopair images) with automatic drivers for displacement of stereoscopic lenses parallel to the stereoscreen, sensor (video camera) for independent definition of three dimensional coordinates of each viewer's eyes position in relation to the common stereoscreen and his own stereoprojector. The system incorporates an auto-corrector connected to the sensor and automatic drives of the stereoscopic lenses. The sensor generates control signal sent to the auto-corrector for the auto-corrector to execute the signal of automatic drive control. The automatic drives automatically continuously dynamically displace the stereoscopic lenses and orientate them in parallel to the stereoscreen for constant matching of the stereo vision focal zones of the stereopair left and right screen images with the viewers' left and right eyes respectively.
The prototype provides for visual comfort of stereo viewing (smaller eye strain and experimentally demonstrated real depth of stereo effect up to 1 km and more when a viewer is placed at a distance of 3 m to the stereoscreen) owing to equalization of the viewer's accommodation efforts and convergence state of the eyes. provides for partial improvement of physical comfort with a possibility for the viewer to move and incline his head in the space of the stereo vision zone (due to the displacement of the projection lenses of the stereoprojectors).
The prototype's disadvantage is small and limited improvement of the stereoscopic comfort. This is conditioned by constructive limits of the stereoscopic lens displacement only in parallel to the stereoscreen which allows small range of the viewer's head displacements along the radius of the stereoscreen of about 100-200 mm (in the limits of the length of the focal zones of the stereo vision ensuring the viewing of full-screen stereoimage). Field of the screen stereoimage vision is limited by small space of the focal zone of viewing of the full-screen stereoimage which limits number and depth of the stereo effect planes proportional to the angle of the field of vision. Different curvature of the left and right frames of the stereopair images increases feeling of stereoscopic discomfort, strain and weariness of the eyes because this increases visible divarication of the conjugate points (any two points of the stereopair left and right frames observed as a single point of the stereoimage) as the eyes focal point moves to the stereoscreen border. Furthermore, harmonization of accommodation (ocular focusing) and eyes convergence (slant of the ocular vision axes) don't correspond to the natural binocular viewing of real objects.
The prototype disadvantages result from the fact that only auto-corrector and automatic drives are used for auto-correction of displacement of the stereoscopic projection lenses relative to the stereoscreen. There aren't provided systems of the viewer's ocular convergence monitoring, systems of video correction of the stereoscreen sphericity and geometrical distortions of the projected frames neither a system of wide-frame stereoscopic projection for provision of prolonged full comfort viewing due to visual dynamic convergence of conjugate points in synchronism with changes of the viewers' ocular convergence and ocular focal point.